A systematic program of measurements related to the hydrogen ion beam in specimen interaction will be carried out, using the magnetic spectrometer system recently completed. Basic experiments comprise determinations, as a function of incident ion energy (10-70 KeV), as a function of target thickness (20-200 Angstrom units and chemical composition (a variety of pure elements and simple chemical compounds), of: a) The rate of energy loss dE/dx and of the fluctuations in such rate (straggling) from the energy loss spectra. b) The elastic scattering cross-sections and ratios of elastic to inelastic scattering cross-sections. c) The fractions of ions which become neutralized during target traversal (charge fractions), and in particular the dependence of such fractions on the hydrogen content of the target specimen. d) The fractions of molecular ions which are transmitted undissociated (or recombined). Such quantities can be extracted from the data collected simultaneously through the various output channels of the STIM. The above determinations will be extended to macromolecules of biological interest such as thymine fluorothymine, cytosine and fluorocytosine, cytochromes, polylysine, quanine, etc. Our ability to obtain electron energy loss spectra as well will enable us to determine important parameters relative to radiation damage under ion bombardment, such as mass loss and structural changes.